Objective lens driving apparatus for optical disc player

ABSTRACT

Disclosed is an objective lens driving apparatus having a holder  9  holding an objective lens  1  and connected to a base  17  through at least four linear members  13,  such that the holder  9  can be moved both in the focussing direction and in the tracking direction orthogonal to the focussing direction through the flexing of the linear members  13.  Undesirable local resonance can be suppressed due to the use of the linear members  13  in support of the holder  9.

FIELD OF THE INVENTION

The present invention relates to an objective lens driving apparatus foruse in an optical disc player which is adapted to optically readinformation from a disc-shaped recording medium by projecting a lightspot onto the medium.

BACKGROUND ART

Known disc players of the kind described incorporate an optical pickupadapted to be moved linearly in the radial direction of a disc. A pickupis provided with an objective lens which is driven both in the focussingdirection and tracking direction thus optically reading an informationrecorded in the disc. In order to attain a highly precise reading of theinformation in this type of optical disc player, therefore, it isnecessary to conduct both focussing control for controlling the distancebetween the objective lens and the information track by moving theobjective lens such as to eliminate any change in the distanceattributable to distortion and oscillation of the disc, and trackingcontrol for moving the objective lens in a manner to follow up theinformation track. These two types of control necessitate an objectivelens driving apparatus capable of driving the objective lens both in thefocussing direction and the tracking direction.

A known objective lens driving apparatus, which has been improved tosome extent, will be explained hereinunder. FIG. 1 is a perspective viewof the known objective lens driving apparatus, while FIG. 2 is anexploded perspective view of the same. An objective lens designated byreference numeral 1 is held by a holder 2. The objective lens 1 ismovably supported by web-like supporting members 4 which are made of aplastic material and fixed both to the holder 2 and a base 3 of theobjective lens driving apparatus. U-shaped yokes 5a, 5b made of amagnetic material are fixed to the base by means of small screws 6a to6d. Permanent magnets 7a, 7b are secured to respective yokes 5a, 5b in amanner to provide magnetic gaps between these permanent magnets and theassociated yokes. Coils 8a, 8b are wound around the holder 2.

This known objective lens driving apparatus operates in a manner whichwill be explained hereinunder.

The levels and polarities of electric currents supplied to the coils 8a,8b are suitably controlled so that the holder 2 is electromagneticallydriven by the electromagnetic forces exerted across the magnetic gapsformed between the permanent magnets 7a, 7b and the yokes 5a, 5b therebymoving the objective lens 1 two-dimensionally within a plane asindicated by arrows in FIG. 1. Consequently, the objective lens 1 ismoved in two directions, i.e., in the focussing direction and in thetracking direction, thus allowing a high accuracy in the reading of theinformation.

In this known objective lens driving apparatus, the objective lens issupported by the web-like supporting members 4 which are adapted to beflexed to permit the movement of the objective lens 1 both in thefocussing direction and the tracking direction. This arrangement iscomplicated and raises the cost of production considerably and is liableto allow local partial resonance which impedes the operation of theapparatus tremendously. Namely, when the supporting members 4 are flexedin the focussing direction, stress is produced not only in the focussingdirection but also in the tracking direction and an undesirable localresonance is caused by the stress acting in the tracking direction.

In this known objective lens driving apparatus, it is necessary thatclearances between the holder 2 and the assemblies of the yokes 5a, 5band permanent magnets 7a, 7b are controlled highly precisely.Furthermore, since the yokes 5a, 5b and the base 3 are formed asseparate parts, there is a fear that the aforementioned gaps may beeliminated due to the sum of the dimensional errors of these parts.Therefore, it is required that these parts be finished within smalltolerances, resulting in a raised cost of production of the parts.

The supporting members 4 in support of the objective lens areconstructed such that the lens is held horizontally when no load isapplied thereto. In the assembled state of the apparatus, therefore, thesupporting members are deflected downwardly due to the weight of thelens and the holder, so that these supporting members tend to sufferfrom a torsional resonance. This problem can be solved by supplying thedriving coils with biasing electric currents such as to raise theobjective lens by the electromagnetic force produced by the biasingelectric currents. This solution, however, causes other problems such aswasteful use of electric power and generation of heat.

DISCLOSURE OF THE INVENTION

Accordingly, an object of the invention is to provide an objective lensdriving device for optical disc players which is improved to reduceundesirable local resonance thereby obviating the above-describedproblems of the prior art.

To this end, the invention provides in its one aspect an objective lensdriving device having a holder to which an objective lens is fixed, abase, and at least four linear members arranged in parallel and fixed attheir both ends to said holder and said base, respectively, whereby saidholder is resiliently supported on said base through said linear membersboth in the focussing direction and tracking direction.

The invention provides in another aspect an objective lens drivingapparatus for an optical disc player comprising: an objective lens; aholder holding the objective lens; a tracking driving coil and afocussing driving coil fixed to the holder; a base; magnets fixed to thebase and disposed in a manner to face the driving coils; and asupporting means having one end fixed to the holder and the other endfixed to the base and supporting the holder movably with respect to thebase; wherein the improvement comprises that the supporting meansexerting a biasing force of a level corresponding to the weights of theobjective lens and the holder such that the centers of the driving coilscorrectly face the centers of the magnets when no electric current issupplied to the driving coils.

In still another aspect of the invention, two or more magnetic yokes areintegrated into a single member so that the troublesome position controlwork is eliminated and the number of the parts is decreased so as toremarkably reduce the production cost of the apparatus.

In a further aspect of the invention, the yokes and the base of theobjective lens driving apparatus is integrated into one body so as toreduce the overall height of the objective lens driving apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 are a fragmentary perspective view of an essential portionof a conventional objective lens driving apparatus and an explodedperspective view of the whole apparatus;

FIGS. 3 and 4 are a perspective view and an exploded perspective view ofan embodiment of the invention;

FIGS. 5a and 5b are illustrations of methods soldering metallic wires inthe embodiment shown in FIGS. 3 and 4;

FIGS. 6a and 6b are gain characteristic charts corresponding to FIGS. 5aand 5b, respectively; and

FIG. 7 is an exploded perspective view of another embodiment of theinvention.

THE BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 3 shows an embodiment of the invention, while FIG. 4 illustratesthe detail of the driving section of the embodiment shown in FIG. 3.

An objective lens 1 is bonded to a holder 9 around which is wound afocussing driving coil 10. A pair of D-shaped tracking driving coils 11are bonded to both lateral sides of the holder 9. Each driving coil hasa linear section constituting an effective driving portion and anothersection which does not contribute to the driving and hence has asemi-circular form for reducing the electric resistance, thus presentinga D-shaped form as a whole.

Four lengths of metallic wire 13 covered by four lengths of rubber tube12 have one of their ends fitting in holes 9a formed in the holder 9 andsoldered to a printed circuit board 14 adhered to the holder 9, whilethe other ends are soldered to another printed circuit board 15 which inturn is fixed to a base 17 by means of a screw 16. The base 17 is madeof a magnetic material and constitute a magnetic circuit in cooperationwith two magnets 18 bonded thereto.

The focussing driving coil 10 and the tracking driving coils 11 aresoldered at their both ends to the printed circuit board 14. The drivingcoils 10 and 11 are electrically connected to four lengths of metallicwire 13 through a copper foil on the printed circuit board 14.

Lead wires 19 are soldered to the printed circuit board 15 andelectrically connected to the lengths of metallic wire 13.

In operation, electric currents are supplied to the focussing drivingcoil 10 or the tracking driving coils 11 through the lead wires 19 andthe lengths of metallic wire 13, so that the holder 9 and hence theobjective lens 1 are driven in the focussing direction or in thetracking direction through the interaction between the electric currentssupplied to the coils and the magnetic fields produced by the magnets18.

In the described embodiment of the invention, since the holder 9 issupported by the lengths of metallic wire 13 both in the focussing andtracking directions, the compliances in both directions are equalized topermit the driving of the objective lens in both directions by an equallevel of the electric power.

Moreover, the metallic wire 13 is not in the form of a plate but is inthe form of a line. So, when the lengths of metallic wire 13 supportingthe holder 9 in the focussing direction are flexed in the samedirection, unnecessary stresses produced in the lengths of metallic wire13 which support the holder 9 in the tracking direction becomeconsiderably small as compared with the prior metallic wire made of aleaf spring. Therefore, detrimental local resonance is reduced.

Furthermore, the cantilever-type supporting structure for the holder 9permits the use of metallic wire 13 having a comparatively largediameter as compared with the case where the holder 9 is supported atits both sides, for attaining an equal level of compliance.Consequently, the length of the metallic wire 13 can be increased toensure highly stiff and reliable resilience of the supporting structurewhile allowing a large stroke of the displacement of the holder 9 ineach direction. Conversely, when the diameter of the metallic wire 13 inthe cantilever-type supporting structure is equal to that of themetallic wire which supports both sides of the holder 9, the efficiencycan be increased due to large compliance.

Therefore, by selecting the optimum diameter of the metallic wire in thelight of the compliance, it is possible to obtain a high efficiency andreliability of the resilient supporting structure. In addition, theinclination of the objective lens 1 is eliminated because the holder 9is always held in parallel with the base 17 during its movement.

It is to be noted also that the inclination or tilt of the movable partcan be adjusted easily because the movable parts as a whole is rotatableabout the screw 16.

Although the described embodiment incorporates four lengths of metallicwire 13 in total, this number is not exclusive and the arrangement maybe such that six lengths of metallic wire, i.e., three lengths forsupporting the holder in one direction and three lengths for the otherdirection, are used for supporting the holder. In addition, instead ofcovering the metallic wire 13 by rubber tube 12, the metallic wire 13and the covering rubber layer can be formed integrally by insertionmolding. In the described embodiment, the printed circuit board 15 isdirectly fixed to the base by a single screw 16. This arrangement may bemodified such that the printed circuit board 15 is secured to the base17 by two or more screws with an intermediary of a rubber layer placedtherebetween, so as to permit position control of the holder 9 not onlyin the focussing and tracking directions but also in the longitudinaldirection.

Preferably, a very straight wire having a high tensile strength andresiliency are used as the metallic wire, such as, for example, phosphorbronze wire, beryllium copper wire, piano wire, stainless steel wire andso forth. The cross-section of the metallic wire may be circular orsquare. Namely, all that is required is that each metallic wire not haveany directivity in two orthogonal directions. The diameter or size ofthe cross-section of the metallic wire should be selected suitably inview of Young's modulus. In normal cases, metallic wire of a diameterbetween 0.1 mm and 0.2 mm are used suitably. Needless to say, linearmembers made of a polymeric material may be used in place of themetallic wire.

FIG. 5 illustrates how the lengths of metallic wire 13 are soldered.

If the soldering is conducted with the holder 9 held in the horizontalposition, the holder 9 is lowered as shown by broken lines in FIG. 6a 5aafter such soldering, due to its weight. In such a case, the holder 9cannot correctly face the magnets 18 so that undesirable torsionalresonance tends to occur. To obviate this problem, in the manufacture ofthe described embodiment of the apparatus, such soldering is conductedwhile holding the holder 9 at a raised position as shown in FIG. 5b,such that, when the holder is lowered by the force of its weight and theweight of the objective lens after the soldering, the driving coils 10and 11 can correctly face the magnets 18, thus eliminating thepossibility of the torsional resonance.

FIG. 6a illustrates the result of measurement of the movement of theobjective lens 1 as observed in the conventional apparatus when thetracking driving coils 11 are supplied with electric currents, whileFIG. 6b shows the result as observed in the apparatus of the invention.As will be seen from FIG. 6a, in the conventional apparatus, the gaincharacteristic involves a peak dip due to the torsional resonance,resulting in a delay of phase. In consequence, the transientcharacteristic is impaired at the resonance frequency. In contrast, theembodiment of the invention is almost free from the peak dip due totorsional resonance, as will be seen from FIG. 6b.

Although in the described embodiment the lengths of metallic wireconstituting the resilient supporting members serve also as electricconductors through which electric current is supplied, the resilientsupporting members may be merely mechanical supporting means withoutelectric conductivity.

FIG. 7 is an exploded perspective view of another embodiment of theobjective lens driving apparatus in accordance with the invention. Inthis Figure, reference numeral 1 designates an objective lens, 20 aholder holding the objective lens 21a to 21b lengths of metallic wirefor supporting the holder, 22a and 22b magnets, 23 a focussing drivingcoil wound on the holder 20, 24 a tracking driving coil constituted byfour D-shaped coils fixed to the holder 20, 25 an integral yoke-baseassembly formed by, for example, sintering from a magnetic material, 2528a wiring substrate, and 26 a holder for locating metallic wires 21a to21b. The holder 26 is secured together with the substrate 25 28to theyoke-base assembly 25 by means of a small screw 27.

The holder 20 is supported by means of four lengths of metallic wire21a, 21b, 21c and 21d, for free movement with respect to the disc-likerecording medium both in the tracking and focussing directions withoutmaking any tilt. Two magnetic gaps are formed between two magnets 22a,22b and the single yoke base 25. The objective lens 1 can be driven bothin the focussing direction and the tracking direction as electriccurrent is supplied to the focussing driving coil 23 and the trackingdriving coil 24 which are fixed to the holder 20.

In this embodiment, since two yokes are integrated with the base, theyoke position control is eliminated to reduce the number of steps in themanufacturing process. For the same reason, the number of the parts isdecreased to eliminate the necessity of small tolerance of the partswhich has been required in the conventional apparatus to obviate thesumming of the dimensional errors of a number of parts. Consequently,the cost of the parts can be reduced remarkably. Furthermore, theconstruction of the objective lens driving apparatus is furthersimplified and, since the fixing of the yokes to the base by screws isunnecessary, the overall height of the objective lens driving apparatusis decreased by a certain amount, e.g., about 2 mm. Furthermore, therigidity of the yokes is increased because they are integrated with thebase, so that the noise attributable to the resonance of the yokes issuppressed to ensure a higher quality of the apparatus.

The bottom of the base can have a considerably complicated configurationprovided that the yoke-base assembly is formed by sintering, so thatguiding for securing the apparatus to another equipment, as well asother functional parts, can be formed on the bottom of the base withoutsubstantial difficulty.

Furthermore, the formation of the yoke and base by the sintered metalpermits a less-expensive mass-production of the parts with highdimensional stability.

Although in the described embodiment the yoke has a substantiallyU-shaped form, this is not exclusive and the yoke can have a formconstituted by a combination of cylinders, as in the case of the yokeswhich are used in speakers. The yoke-base assembly, which has beendescribed as being a sintered body, may be formed by press work from asheet metal.

INDUSTRIAL APPLICABILITY

As has been described, in the objective lens driving apparatus of theinvention, the holder holding the objective lens is supported on thebase through at least four lengths of metallic wire such that thedeflection of these lengths of metallic wire allow the holder to move intwo orthogonal directions. Consequently, the invention remarkablysimplifies the construction of the objective lens driving apparatus andreduces the cost of the same, while suppressing occurrence ofundesirable local resonance.

It is to be noted also that the torsional resonance can be preventedwhile reducing the electric power consumption and the heat generation,because the tracking driving coils can correctly face the magnetswithout requiring application of any biasing electric current. This inturn ensures superior transient characteristics when control iscommenced, and completely eliminates the unstable operation which isattributable to torsional resonance.

In addition, by integrating the pair of yokes, it is possible to reducethe size of the objective lens driving apparatus and to ensure a highprecision of operation of the apparatus, without necessitating any workfor controlling the positions of the yokes.

What is claimed is:
 1. An objective lens driving apparatus for anoptical disc player, comprising a base, a holder holding an objectivelens, a supporting means for movably supporting said holder on saidbase, and a driving means for driving said holder both in a focussingdirection corresponding to the optical axis of said objective lens andin a tracking direction substantially traverse to the focussingdirection, said supporting means including at least four parallel linearmembers which are fixed at one of their ends to said base and at theirother end to said holder, each said linear member being resilient in thefocussing direction and in the tracking direction, so as to make saidholder freely movable in the focussing direction and in the trackingdirection, whereby all of said respective linear members themselves flexin the driving direction of said driving means to allow said holder tomove when said holder is driven by said driving means in the focussingdirection and in the tracking direction.
 2. An objective lens drivingapparatus for an optical disc player according to claim 1, comprising abase, a holder holding an objective lens, a supporting means for movablysupporting said holder on said base, and a driving means for drivingsaid holder both in a focussing direction corresponding to the opticalaxis of said objective lens and in a tracking direction substantiallytransverse to the focussing direction, said supporting means includingat least four parallel linear members which are fixed at one of theirends to said base and at their other end to said holder, each saidlinear member being resilient in the focussing direction and in thetracking direction, so as to make said holder freely movable in thefocussing direction and in the tracking direction, whereby all of saidrespective linear members themselves flex in the driving direction ofsaid driving means to allow said holder to move when said holder isdriven by said driving means in the focussing direction and in thetracking direction, wherein said linear members comprise elongatedmetallic wire.
 3. An objective lens driving apparatus for an opticaldisc player according to claim 2, 32 or 39, wherein said metallic wireis one having high tensile strength.
 4. An objective lens drivingapparatus for an optical disc player according to claim 1 32 or 39,wherein said linear members are made of a polymeric material.
 5. Anobjective lens driving apparatus for an optical disc player according toclaim 1 2, 32 or 39, wherein a viscoelastic material is deposited ontothe outer surfaces of said linear members.
 6. An objective lens drivingapparatus as in claim 3, wherein said metallic wire comprises a materialwhich is selected from the group consisting of phosphor bronze wire,beryllium copper wire, piano wire and stainless steel wire.
 7. Anobjective lens driving apparatus for an optical disc player, comprisingan objective lens; a holder holding said objective lens; a trackingdriving coil and a focussing driving coil fixed to said holder; a base;magnets fixed to the said base and disposed to face said driving coils;and a flexible supporting means in the form of at least four linearmembers which are parallel to one another each of which is resilient inthe focussing direction and in the tracking direction and having one endfixed to said holder and another end fixed to said base and supportingsaid holder movably with respect to said base; said supporting meansapplying a biasing force having a magnitude corresponding to the weightsof said objective lens and said holder such that the centers of saiddriving coils correctly face the centers of said magnets when noelectric current is supplied to said driving coils.
 8. An objective lensdriving apparatus for an optical disc player according to claim 7,comprising an objective lens; a holder holding said objective lens; atracking driving coil and a focussing driving coil fixed to said holder;a base; magnets fixed to said base and disposed to face said trackingand focussing driving coils; and a flexible supporting means in a formof at least four linear members which are parallel to one another andeach of which is resilient in a focussing direction and in a trackingdirection and having one end fixed to said holder and another end fixedto said base and supporting said holder movably with respect to saidbase; said supporting means applying a biasing force having a magnitudecorresponding to the weights of said objective lens and said holder suchthat the centers of said tracking and focussing driving coils correctlyface centers of said magnets when no electric current is supplied tosaid tracking and focussing driving coils, wherein said linear memberscomprise elongated metallic wire.
 9. An objective lens driving apparatusfor an optical disc player according to claim 8, wherein said metallicwire is one having high tensile strength.
 10. An objective lens drivingapparatus as in claim 9, wherein said metallic material is selected fromthe group consisting of phosphor bronze wire, beryllium copper wire,piano wire and stainless steel wire.
 11. An objective lens drivingapparatus for an optical disc player according to claim 7, wherein saidlinear members are made of a polymeric material.
 12. An objective lensdriving apparatus for an optical disc player according to claim 7,wherein a viscoelastic material is deposited onto the outer surfaces ofsaid linear members.
 13. An objective lens driving apparatus for anoptical disc player, comprising an objective lens; a holder holding saidobjective lens; a tracking driving coil and a focussing driving coilfixed to said holder; a base; a pair of magnets fixed to said base anddisposed to face respective driving coils; a pair of yokes integrallyformed of a magnetic material and disposed in the vicinity of saidmagnets; and a cantilever supporting means having one end fixed to saidholder and another end fixed to said base and supporting said holdermovably with respect to said base.
 14. An objective lens drivingapparatus for an optical disc player according to claim 13, wherein saidpair of yokes and said base are constructed as a unit with each other.15. An objective lens driving apparatus for an optical disc playercomprising a base, a holder holding an objective lens, a supportingmeans for movably supporting said holder on said base, and a drivingmeans for driving said holder both in the focussing direction and in thetracking direction, said supporting means comprising at least fourparallel linear members which comprise a conductive metallic materialand which are flexible in the focussing direction and in the trackingdirection and are fixed at one of their ends to said base and at theirother end to said holder, and said driving means comprises magnet meansprovided on said base and driving coils provided on said holder, so thatsaid holder is driven in two orthogonal directions by the interactionbetween said magnet means and said driving coils, said driving coilsbeing electrically connected at one of their ends to said metallicmaterial such that said driving coils are supplied with electric currentthrough said metallic material.
 16. An objective lens driving apparatusfor an optical disc player, comprising an objective lens; a holderholding said objective lens; a tracking driving coil and a focussingdriving coil fixed to said holder; a base; magnet means fixed to saidbase and disposed to face said driving coils; and linear memberscomprising a conductive metallic material and having one end fixed tosaid holder and the other end fixed to said base and supporting saidholder movably with respect to said base, said tracking and focussingdriving coils being electrically connected at both of their ends to saidmetallic material so that said driving coils are supplied with electriccurrent through said metallic material, said supporting means applying abiasing force having a magnitude corresponding to the weights of saidobjective lens and said holder such that the centers of said drivingcoils correctly face the centers of said magnets when no electriccurrent is supplied to said driving coils.
 17. An objective lens drivingapparatus for an optical disc player according to claim 15, wherein saidmetallic material is one having high tensile strength.
 18. An objectivelens driving apparatus as in claim 17, wherein said metallic material isselected from the group consisting of phosphor bronze wire, berylliumcopper wire, piano wire and stainless steel wire.
 19. An objective lensdriving apparatus for an optical disc player according to claim 15,wherein a viscoelastic material is deposited onto the outer surface ofsaid supporting means.
 20. An objective lens driving apparatus for anoptical disc player according to claim 16, wherein said metallicmaterial is one having high tensile strength.
 21. An objective lensdriving apparatus as in claim 20, wherein said metallic material isselected from the group consisting of phosphor bronze wire, berylliumcopper wire, piano wire and stainless steel wire.
 22. An objective lensdriving apparatus for an optical disc player according to claim 16,wherein a viscoelastic material is deposited onto the outer surface ofsaid supporting means.
 23. An objective lens driving apparatus for anoptical disc player, comprising a base, a holder holding an objectivelens, a cantilever supporting means for movably supporting said holderon said base, and a driving means for driving said holder in a focussingdirection and in the tracking direction, said supporting meanscomprising a conductive metallic material having one end fixed to saidbase and the other end fixed to said holder, and said driving meanscomprising magnets provided on said base and driving coils provided onsaid holder, so that said holder is driven in two orthogonal directionsby the interaction between said magnets and said driving coils, saiddriving coils being electrically connected at their opposite ends tosaid supporting means constituted by said conductive metallic materialsuch that said driving coils are supplied with electric current throughsaid supporting means.
 24. An objective lens driving apparatus for anoptical disc player according to claim 23, wherein said magnets providedon said base are disposed to face said driving coils provided on saidholder, and said supporting means applies a biasing force having amagnitude corresponding to the weights of said objective lens and saidholder such that the centers of said driving coils correctly face thecenters of said magnets when no electric current is supplied to saiddriving coils.
 25. An objective lens driving apparatus for an opticaldisc player, comprising an objective lens, a holder holding saidobjective lens, a tracking driving coil and a focussing driving coilfixed to said holder, a base, magnets fixed to said base and disposed toface said respective driving coils, and a supporting means comprisingfour or more parallel linear members which are fixed at one of theirends to said base and at their other end to said holder, each of saidlinear members being resilient in the focussing direction and in thetracking direction.
 26. An objective lens driving apparatus for anoptical disc player, comprising an objective lens; a holder holding saidobjective lens; a tracking driving coil and a focussing driving coilfixed to said holder; a base; a pair of magnets fixed to said base anddisposed to face respective ones of said tracking and focussing drivingcoils; a pair of yokes integrally formed of a magnetic material anddisposed in a vicinity of said magnets; and supporting means includingat least four parallel linear members each having one end fixed to saidholder and another end fixed to said base and supporting said holdermovably with respect to said base, wherein said linear members comprisemetallic wire.
 27. An objective lens driving apparatus for an opticaldisc player, comprising a base, a holder holding an objective lens, asupporting means for movably supporting said holder on said base, and adriving means for driving said holder both in a focussing direction andin a tracking direction, said supporting means comprising at least fourparallel linear members each of which comprises a conductive metallicmaterial and is flexible in the focussing direction and in the trackingdirection and are fixed at one of their ends to said base and at theirother end to said holder, and said driving means comprises magnet meansprovided on said base and driving coils provided on said holder, so thatsaid holder is driven in two orthogonal directions by interactionbetween said magnet means and said driving coils, said driving coilsbeing electrically connected at one of their ends to said metallicmaterial such that said driving coils are supplied with electric currentthrough said metallic material, wherein said linear members comprisemetallic wire.
 28. An objective lens driving apparatus for an opticaldisc player, comprising an objective lens; a holder holding saidobjective lens; a tracking driving coil and a focussing driving coilfixed to said holder; a base; magnet means fixed to said base anddisposed to face said tracking and focussing driving coils; and linearmembers each comprising a conductive metallic material and having oneend fixed to said holder and the other end fixed to said base andsupporting said holder movably with respect to said base, said trackingand focussing driving coils being electrically connected at both oftheir ends to said metallic material so that said tracking and focussingdriving coils are supplied with electric current through said metallicmaterial, said supporting means applying a biasing force having amagnitude corresponding to the weights of said objective lens and saidholder such that centers of said tracking and focussing driving coilscorrectly face centers of said magnets when no electric current issupplied to said tracking and focussing driving coils, wherein likelinear members comprise metallic wire.
 29. An objective lens drivingapparatus for an optical disc player, comprising a base, a holderholding an objective lens, supporting means including at least fourparallel linear members each for movably supporting said holder on saidbase, and a driving means for driving said holder in a focussingdirection and in a tracking direction, said linear members of saidsupporting means each comprising a conductive metallic material havingone end fixed to said base and the other end fixed to said holder, andsaid driving means comprising magnets provided on said base and drivingcoils provided on said holder, so that said holder is driven in twoorthogonal directions by interaction between said magnets and saiddriving coils, said driving coils being electrically connected at theiropposite ends to said linear members of said supporting meansconstituted by said conductive metallic material such that said drivingcoils are supplied with electric current through said supporting means,wherein said linear members comprise metallic wire.
 30. An objectivelens driving apparatus for an optical disc player, comprising anobjective lens, a holder holding said objective lens, a tracking drivingcoil and a focussing driving coil fixed to said holder, a base, magnetsfixed to said base and disposed to face said respective tracking andfocussing driving coils, and a supporting means comprising four or moreparallel linear members which are each fixed at one of their ends tosaid base and at their other end to said holder, each of said linearmembers being resilient in a focussing direction and in a trackingdirection, wherein said linear members comprise metallic wire.
 31. Anobjective lens driving apparatus for an optical disc player according toclaim 2, 32 or 39, wherein said metallic wire is elongated.
 32. Anobjective lens driving apparatus for an optical disc player, comprisinga base, a holder holding an objective lens, a supporting means formovably supporting said holder on said base, and a driving means fordriving said holder both in a focussing direction corresponding to theoptical axis of said objective lens and in a tracking directionsubstantially transverse to the focussing direction, said supportingmeans including at least four parallel linear members which are eachfixed at one of their ends to said base and at their other end to saidholder, each said linear member being resilient in the focussingdirection and in the tracking direction, so as to make said holderfreely movably in the focussing direction and in the tracking direction,whereby all of said respective linear members themselves flex in thedriving direction of said driving means to allow said holder to movewhen said holder is driven by said driving means in the focussingdirection and in the tracking direction, wherein said at least fourparallel linear members have a substantially uniform cross-sectionalshape along an axis thereof.
 33. An objective lens driving apparatus foran optical disc player, comprising an objective lens; a holder holdingsaid objective lens; a tracking driving coil and a focussing drivingcoil fixed to said holder; a base; magnets fixed to said base anddisposed to face said tracking and focussing driving coils; and aflexible supporting means in a form of at least four linear memberswhich are parallel to one another and each of which is resilient in afocussing direction and in a tracking direction and having one end fixedto said holder and another end fixed to said base and supporting saidholder movably with respect to said base; said supporting means applyinga biasing force having a magnitude corresponding to the weights of saidobjective lens and said holder such that the centers of said trackingand focussing driving coils correctly face centers of said magnets whenno electric current is supplied to said tracking and focussing drivingcoils, wherein said at least four parallel linear members have asubstantially uniform cross-sectional shape along an axis thereof. 34.An objective lens driving apparatus for an optical disc player,comprising an objective lens; a holder holding said objective lens; atracking driving coil and a focussing driving coil fixed to said holder;a base; a pair of magnets fixed to said base and disposed to facerespective ones of said tracking and focussing driving coils; a pair ofyokes integrally formed of a magnetic material and disposed in avicinity of said magnets; and supporting means including at least fourparallel linear members each having one end fixed to said holder andanother end fixed to said base and supporting said holder movably withrespect to said base, wherein said at least four parallel linear membershave a substantially uniform cross-sectional shape along an axisthereof.
 35. An objective lens driving apparatus for an optical discplayer, comprising a base, a holder holding an objective lens, asupporting means for movably supporting said holder on said base, and adriving means for driving said holder both in a focussing directioncorresponding and in a tracking direction, said supporting meanscomprising at least four parallel linear members each of which comprisea conductive metallic material and is flexible in the focussingdirection and in the tracking direction and are fixed at one of theirends to said base and at their other end to said holder, and saiddriving means comprises magnet means provided on said base and drivingcoils provided on said holder, so that said holder is driven in twoorthogonal directions by interaction between said magnet means and saiddriving coils, said driving coils being electrically connected at one oftheir ends to said metallic material such that said driving coils aresupplied with electric current through said metallic material, whereinsaid at least four parallel linear members have a substantially uniformcross-sectional shape along an axis thereof.
 36. An objective lensdriving apparatus for an optical disc player, comprising an objectivelens; a holder holding said objective lens; a tracking driving coil anda focussing driving coil fixed to said holder; a base; magnet meansfixed to said base and disposed to face said tracking and focussingdriving coils; and linear members each comprising a conductive metallicmaterial and having one end fixed to said holder and the other end fixedto said base and supporting said holder movably with respect to saidbase, said tracking and focussing driving coils being electricallyconnected at both of their ends to said metallic material so that saidtracking and focussing driving coils are supplied with electric currentthrough said metallic material, said supporting means applying a biasingforce having a magnitude corresponding to the weights of said objectivelens and said holder such that centers of said tracking and focussingdriving coils correctly face centers of said magnets when no electriccurrent is supplied to said tracking and focussing driving coils,wherein said linear members have a substantially uniform cross-sectionalshape along an axis thereof.
 37. An objective lens driving apparatus foran optical disc player, comprising a base, a holder holding an objectivelens, supporting means including at least four parallel linear memberseach for movably supporting said holder on said base, and a drivingmeans for driving said holder in a focussing direction and in a trackingdirection, said linear members of said supporting means each comprisinga conductive metallic material having one end fixed to said base and theother end fixed to said holder, and said driving means comprisingmagnets provided on said base and driving coils provided on said holder,so that said holder is driven in two orthogonal directions byinteraction between said magnets and said driving coils, said drivingcoils being electrically connected at their opposite ends to said linearmembers of said supporting means constituted by said conductive metallicmaterial such that said driving coils are supplied with electric currentthrough said supporting means, wherein said at least four parallellinear members have a substantially uniform cross-sectional shape alongan axis thereof.
 38. An objective lens driving apparatus for an opticaldisc player, comprising an objective lens, a holder holding saidobjective lens, a tracking driving coil and a focussing driving coilfixed to said holder, a base, magnets fixed to said base and disposed toface said respective tracking and focussing driving coils, and asupporting means comprising four or more parallel linear members whichare each fixed at one of their ends to said base and at their other endto said holder, each of said linear members being resilient in afocussing direction and in a tracking direction, wherein said four ormore parallel linear members have a substantially uniformcross-sectional shape along an axis thereof.
 39. An objective lensdriving apparatus for an optical disk player, comprising a base, aholder holding an objective lens, a supporting means for movablysupporting said holder on said base, and a driving means for drivingsaid holder both in a focussing direction corresponding to the opticalaxis of said objective lens and in a tracking direction substantiallytransverse to the focussing direction, said supporting means includingat least four parallel linear members which are each fixed at one oftheir ends to said base and at their other end to said holder, each saidlinear member being resilient in the focussing direction and in thetracking direction, so as to make said holder freely movably in thefocussing direction and in the tracking direction, whereby all of saidrespective linear members themselves flex in the driving direction ofsaid driving means to allow said holder to move when said holder isdriven by said driving means in the focussing direction and in thetracking direction, wherein each of said linear members has nodirectivity in two orthogonal directions.
 40. An objective lens drivingapparatus for an optical disk player, comprising an objective lens; aholder holding said objective lens; a tracking driving coil and afocussing driving coil fixed to said holder; a base; magnets fixed tosaid base and disposed to face said tracking and focussing drivingcoils; and a flexible supporting means in a form of at least four linearmembers which are parallel to one another and each of which is resilientin a focussing direction and in a tracking direction and having one endfixed to said holder and another end fixed to said base and supportingsaid holder movably with respect to said base; said supporting meansapplying a biasing force having a magnitude corresponding to the weightsof said objective lens and said holder such that the centers of saidtracking and focussing driving coils correctly face centers of saidmagnets when no electric current is supplied to said tracking andfocussing driving coils, wherein each of said linear members has nodirectivity in two orthogonal directions.
 41. An objective lens drivingapparatus for an optical disk player, comprising an objective lens; aholder holding said objective lens; a tracking driving coil and afocussing driving coil fixed to said holder; a base; a pair of magnetsfixed to said base and disposed to face respective ones of said trackingand focussing driving coils; a pair of yokes integrally formed of amagnetic material and disposed in a vicinity of said magnets; andsupporting means including at least four parallel linear members eachhaving one end fixed to said holder and another end fixed to said baseand supporting said holder movably with respect to said base, whereineach of said linear members has no directivity in two orthogonaldirections.
 42. An objective lens driving apparatus for an optical diskplayer, comprising a base, a holder holding an objective lens, asupporting means for movably supporting said holder on said base, and adriving means for driving said holder both in a focussing direction andin a tracking direction, said supporting means comprising at least fourparallel linear members each of which comprises a conductive metallicmaterial and is flexible in the focussing direction and in the trackingdirection and are fixed at one of their ends to said base and at theirother to said holder, and said driving means comprises magnet meansprovided on said base and driving coils providing on said holder, sothat said holder is driven in two orthogonal directions by interactionbetween said magnet means and said driving coils, said driving coilsbeing electrically connected at one of their ends to said metallicmaterial such that said driving coils are supplied with electric currentthrough said metallic material, wherein each of said linear members hasno directivity in two orthogonal directions.
 43. An objective lensdriving apparatus for an optical disc player, comprising an objectivelens; a holder holding said objective lens; a tracking driving coil anda focussing driving coil fixed to said holder; a base; magnets meansfixed to said base and disposed to face said tracking and focussingdriving coils; and linear members each comprising a conductive metallicmaterial and having one end fixed to said holder and the other end fixedto said base and supporting said holder movably with respect to saidbase, said tracking and focussing driving coils being electricallyconnected at both of their ends to said metallic material so that saidtracking and focussing driving coils are supplied with electric currentthrough said metallic material, said supporting means applying a biasingforce having a magnitude corresponding to the weights of said objectivelens and said holder such that centers of said tracking and focussingdriving coils correctly face centers of said magnets when no electriccurrent is supplied to said tracking and focussing driving coils,wherein each of said linear members has no directivity in two orthogonaldirections.
 44. An objective lens driving apparatus for an optical diskplayer, comprising a base, a holder holding an objective lens,supporting means including at least four parallel linear members eachfor movably supporting said holder on said base, and a driving means fordriving said holder in a focussing direction and in a trackingdirection, said linear members of said supporting means each comprisinga conductive metallic material having one end fixed to said base and theother end fixed to said holder, and said driving means comprisingmagnets provided on said base and driving coils provided on said holder,so that said holder is driven in two orthogonal directions byinteraction between said magnets and said driving coils, said drivingcoils being electrically connected at their opposite ends to said linearmembers of said supporting means constituted by said conductive metallicmaterial such that said driving coils are supplied with electric currentthrough said supporting means, wherein each of said linear members hasno directivity in two orthogonal directions.
 45. An objective lensdriving apparatus for an optical disk player, comprising an objectivelens, a holder holding said objective lens, a tracking driving coil anda focussing driving coil fixed to said holder, a base, magnets fixed tosaid base and disposed to face said respective tracking and focussingdriving coils, and a supporting means comprising four or more parallellinear members which are each fixed at one of their ends to said baseand at their other end to said holder, each of said linear members beingresilient in a focussing direction and in a tracking direction, whereineach of said linear members has no directivity in two orthogonaldirections.